BrRRG affects leaf size by regulating cell cycle gene expression in Chinese cabbage

1. RETARDED ROOT GROWTH ( BrRRG ) is the gene responsible for defective leaf and root development in the mini24 mutant. 2. Identification of BrRRG as a key regulator controlling leaf size via E2Fa and cell-cycle genes in Chinese cabbage. Chinese cabbage ( Brassica rapa subsp. pekinensis ) is a significant leafy vegetable in the Brassica genus of the Brassicaceae family. The size of edible leaves is an essential trait that determines its economic and nutritional values. However, current understanding of leaf development in Chinese cabbage is limited. Here, through forward genetic analyses of the mutant mini24 with defective leaf and root development, we identified the BrRRG gene, which regulates cell division in Chinese cabbage by map-based cloning. We demonstrated that BrRRG impacts leaf size by regulating the expression of E2Fa transcription factors and cell cycle-related genes in Chinese cabbage. Furthermore, BrRRG was found to modulates Chinese cabbage responds to IAA hormones and cytokinins, revealing distinct regulatory mechanisms by which BrRRG controls underground root and aboveground leaf development. Thus, these results suggest that BrRRG mutant causes damage to plant growth and development in Chinese cabbage.